This disclosure relates to novel alkyl, cycloalkyl and aralkyl azo compounds containing an .alpha.-hydroperoxy group, and the alkali metal or alkaline earth metal salts thereof; to processes for their preparation; and to their use as polymerization initiators for ethylenically unsaturated monomers and as curing agents for polyester resin compositions.
To the best of applicants' knowledge, there are no known examples of aliphatic-azo compounds as defined by structure I. Aromatic-azoalkanes containing .alpha.-hydroperoxy groups are reported in R. Criegee and G. Lohaus, Chem. Ber. 84, 219 (1951); and in F. Minisci, Gazz. Chim. ital. 89, 626 (1959). K. H. Pausacker, J. Chem. Soc., 3478 (1950); A. J. Bellamy and R. D. Guthrie, J. Chem. Soc. 2788 (1965); G. J. Karabatsos et al., J.A.C.S., 85, 3627 (1963); and H. C. Yas et al., J. Org. Chem. 30, 2832 (1965) have studied auto-oxidation of arylhydrazones.
U.S. Pat. No. 3,278,304 describes a process for the photopolymerization of ethylenically unsaturated organic compositions, using azo-hydroperoxides as initiators. While only aromatic azo-hydroperoxides (derived from aromatic hydrazones) are used in the working examples, they state that aliphatic azo-hydroperoxides are suitable and that "all these azohydroperoxides are manufactured according to known methods." Applicants, however, do not know of the previous existence of any such aliphatic azohydroperoxides or of any known method for their preparation. Since aromatic azo compounds are normally much more stable than the corresponding aliphatic azo compounds which are highly susceptible to decomposition, it is submitted that the subject patent does not give sufficient information to suggest how such compounds might be prepared.